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Old 10-31-2014, 04:41 AM   #1
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Default Rear Head to Block Oil Leak Fix (no teardown)

I rebuilt my 7MGTE engine with a Victor Reinz head Gasket, a Silver Seal 20 tho shim gasket, and ARP studs/nuts. I torqued and re-torqued the head to 90 foot pounds. After driving awhile, I was surprised to find that the old oil leak in the back corner on the passenger side was there haunting me from like years before. It tends to leak there because there is a drain passage that drains oil from the back half of both cams down into the block and its a hard point in the gasket to crush. It wasn't a bad leak, just annoying. It would drip between the head / block and collect in a drop on the back corner of the EGR cooler and drip down on to the coolant bypass pipe and on the block. From there are it would travel further down and eventually find its way on to the exhaust pipe support bracket. I put a spot of silicone on the bracket lower edge so that the oil would drip onto the ground before making it to the exhaust pipe clamp.

I thought of a way to fix the leak without taking the head off and ruining the gasket, which has proven to be successful. It involves lining the oil return passage where the aluminum head, gaskets, iron block meet with Permatex Ultra Black silicone, which has high oil resistance. The problem is that the car has been run and it's an oily mess in the drain passage that has to be removed before applying the silicone to stick and cure hard. This is how I did it. I let the car sit for a day to allow the oil to drain down as much as possible. Take off the valve covers and use a syringe or towels to remove as much oil as possible from the back set of cam buckets on both sides. Pack those places and the galley below with new pieces of paper towel to stop more oil from flowing to the drain hole. There is a back passage between the 2 camshafts. Pack that also. Just remember to REMOVE ALL THE PAPER TOWELS at the end of the repair otherwise there could be engine damage. Now that oil oozing toward the drain is greatly reduced, it's time to cleanup that area. First take dry paper towel and sop up any surface oil. A shop or dental tweezers really helps when doing all this. Next spray some carburetor cleaner on paper towel and repeat the process around the drain hole. Have a fan blowing somewhere nearby so you don't breathe the stuff and put the wet pieces in a zip-lock bag. I used what I think is a kitchen utensil that has a round 1/2 inch brush on the end like a bottle brush. Wrapping a "select a sheet" size piece of Bounty paper towel around it makes it snug in the hole. See photos. The interface where they all meet is only about 3 inches below the top of the hole. I chased the oil down the hole using a short stray carburetor cleaner. Wait a minute. First I did a couple of dry towels twisting slowly going in and out. Then I did a couple of carburetor cleaner wet towels the same way. Then finished with a couple of dry ones. Next put a dry paper towel around the brush and put in the hole and leave it there to see if any oil is oozing to the hole. It's OK if the top of the hole gets a oil ring on the towel. It must not flow down into the hole though. It only takes about 1/2 of the towel in the hole in all this, the rest should be above it so it can be pulled out with the brush. I changed the towel every 5 to 10 minutes until the oil ring on the towel got less and stopped. Now it's time to apply the Permatex Ultra Black silicone. I have an inexpensive bore scope that fit into the hole. I could see there was a slight ledge where head, gaskets, and block met. That is the critical area where the sealant needs to be applied to be effective. I used a flat plastic swizzle stick with a ball end to "feel" where the ledge was and noted how deep that was. Don't drop the stick! What I did was to put a small blob of silicone on the ball end and slightly above it then try to center down the drain hole until I got to that point where noted how deep it was before. Then I pushed to one side of the wall to feel for the ledge. When I found it then I would go in a circle a little bit above and a little bit below the ledge. I did this 4 times then I checked it with the bore scope. I thought later another way to do it would be to put silicone on one side of the ball and then drag the dry side down the wall until you felt the ledge and put it to the other side going in a circle, then repeat again going down the opposite wall doing both twice. I put a paper towel plug in the drain hole and let it is set up overnight. I also sealed the back center casting plug behind the last spark plug which was leaking a little bit of oil down into the spark plug plug hole. Ultra Black silicone on the threads in the head and under the center cover did the trick. Harbor Freight has a nice inexpensive set of hex sockets. The size is 14mm hex and 1/2 inch for the drive. The next day when all the silicone has set up its time remove every bit of paper towel that held the oil back. Don't miss any of it especially between the camshafts where that hex plug is. Permatex Ultra Black silicone is also great to seal the valve cover gasket and the crank case ventilation hose by the oil cap. A little goes a long way. I use Permatex red thread locker on the valve cover bolts since I have Allen heads. Original Philips bolts probably you should use the blue Permatex thread locker. The way I check for my oil leak is with engine cold enough to take a piece of paper towel and wipe behind under EGR cooler on the passenger side where the head meets the block and on the coolant bypass pipe under the back half of the exhaust manifold and to look at the block there for past drips on the black paint. After driving for a few days of the amount of oil on the wipe towel has tailed off to nothing. Leak Fixed!

Another troublesome spot is the power steering pump. I rigged up a aluminum foil catch cup that hugs the bottom of the pump and used a small magnet to hold in place. No more drips onto the oil cooler hoses.
While down there, take a look up at the bottom water pump weep hole for any sign of the pump seal going out.
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Last edited by Bru; 11-13-2014 at 05:59 PM.
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